You may have heard the term "white graphite" used in the manufactured ceramics industry. If so, then you're already familiar with the material known as boron nitride ceramic or simply boron nitride. The material resembles graphite in many ways save for its white color, which is where it gets its nickname.
However, boron nitride is a substance in and of itself. It has exceptional electrical insulating properties unlike traditional graphite and is superior in many ways to both conventional and other engineered ceramics. To put it simply, it's a great material for your high-temp and high-stress manufacturing process. We'll explain why.
What is Boron Nitride & What Makes It Unique?
Boron nitride ceramic is what is known as an "engineered" ceramic, which gives it enhanced characteristics that put it above conventional ceramic. These characteristics make it a great material for use in high-stress environments commonly found in laboratories and factories.
Boron nitride is exceptional even to other synthetic ceramics because it has a unique crystal structure that resembles graphite. For this reason, hexagonal boron nitride shares the outstanding mechanical properties of graphite such as a high degree of "lubricity", which is a measure of the reduction in friction.
How Is Boron Nitride Manufactured?
It's quite common to find boron nitride sheets; machining boron nitride ceramic is a simple process, which makes it a versatile material that can be tailored to almost any process. Beyond that, it can be manufactured as a powder, much like the graphite powder you would find in the toolbox of a locksmith.
Boron nitride powder is made by reacting either boron trioxide or boric acid with either ammonia or urea in a nitrogen atmosphere. The powder form of boron nitride has many uses but in the ceramics industry, it is common to find "hot-pressed" boron nitride made into sheets and shapes or into "cubic boron nitride", which is analogous to diamond.
What Are the Properties of Boron Nitride?
Boron nitride has all of the common properties of an engineered ceramic with a few exceptions that make it a superior material:
Outstanding thermal conductivity: boron nitride's natural thermal conductivity makes it a great heat sink while minimizing thermal wear-and-tear even at extremely high temperatures.
One of the finest electrical insulators: whether you call it "dielectric constant" or "relative permittivity", boron nitride is a great electrical insulator with a consistent rating across the board.
Great thermal shock resistance: the thermal management properties of boron nitride are outstanding. It has a naturally low thermal expansion and a high chemical inertness, which means it reacts very little to extremely high or low temperatures or temperature changes
What Are the Most Common Applications of Boron Nitride?
Boron nitride comes in three forms: hexagonal boron nitride, cubic boron nitride, and amorphous nitride. Each of these forms has its own application:
Manufacturing parts: through the "hot press" process, hexagonal boron nitride can be pressed into sheets as well as custom parts for various manufacturing needs.
Extreme temperature lubricant: hexagonal boron nitride is an exceptional lubricant at both low and high temperatures. Due to its low electrical conductivity and natural chemical inertness, hexagonal BN is used often in processes where these properties are required.
Insoluble abrasive: cubic boron nitride is, for all intents and purposes, structurally similar to a diamond. However, because it's an engineered material is has enhanced qualities such as insolubility in iron, nickel or other related alloys, and high temperatures, which diamond lacks.
There are many more applications for BN; it's an incredibly versatile substance. From nanosheets to laser printers, BN can be found in the most common and uncommon applications around the world.
What Are the Various Grades of Boron Nitride?
There are 6 grades of boron nitride used in manufacturing. Each grade has its own set of properties, which makes it unique.
AX05 Grade: At over 99.7% pure, this is the highest purity of BN. It can be used in both inert or vacuum environments in temperatures exceeding 2,000C. AX05 BN is great for processes requiring high temperature and high corrosion resistance.
A Grade: This is the oldest form of hot-pressed boron nitride. It's still a relevant factor in the industry due to its continued use in legacy semiconductor equipment, which still needs to be maintained and repaired.
HP Grade: We think of this as the "jack-of-all-trades" grade of BN. It has consistent performance across the board from low thermal expansion, high thermal shock resistance, and excellent machinability. HP BN can withstand temperatures over 1,000C.
HPL Grade: This grade is very similar to the HP grade with one exception; a slightly higher functional temperature range.
M26/M Grade: Perhaps the most unique form of BN, M26/M brings with it the highest machinability factor and increased resistance to moisture.
ZBSN Grade: While hexagonal BN is typically a "soft" metal, ZBSN is fortified with zirconia, giving it the typical properties of hBN with increased hardness.